Firing pin of light weight material, such as aluminum or titanium



Oct 2, 1962 c. HUBBARD ETAL 3,056,226

FIRING PIN oF LIGHT WEIGHT MATERIAL, sUcH As ALUMINUM 0R TITANIUM Filed Aug. 20, 1959 6I Z 74\ /8\ /i0 f ,"7 I l 1 8 y//f/c/:c/Ejg llllllllll// T- *r/ A /7 m//l/Zsec ands nite gigi@ This invention relates to explosive operated devices such as guns, and more particularly to a percussive tiring mechanism for a breech loading firearm, wherein primed cartridge cases of llixed ammunition are set oft by release of a tiring pin of the type impelled by a cocked spring upon engagement of the tip of the driven pin with the percussion cap or primer mounted in the base of the cartridge case.

In heretofore known tiring mechanisms `of the bolt action type, there occasionally arises a problem of ignition, particularly with certain types of cartridges. Percussive ignition requires that there be backing of the primer. This is provided by the manner in which the cartridge is constructed for supporting the primer and in which the cartridge is seated in the cartridge chamber, as well as by the inertia of the entire cartridge. Furthermore, the sensitivity of a percussion primer to ignition is influenced by a number of other factors among which is the total energy of percussion as well as the configura- -tion of the tiring tip, the latter of which influences the method of delivery of the energy of the bolt action system which consists of the tiring pin and its spring. For any given caliber of weapon, the pin, the pin point shape and the spring are proportioned to obtain the best operation ofthe firing mechanism. When, however, the caliber of the weapon and cartridge becomes quite small, and especially when the cartridge chamber is small in proportion to the bore of the gun, it becomes increasingly difiicult to design the components so as to obtain reliable operation characterized Iby substantial freedom from mislires. Shotshells, too, may lack the same type of freedom from mis'lires. For example, at calibers below about .50 of an inch and down to around .22 caliber, the heretofore conventional tiring mechanism of this type shows that its limits of consistent effectiveness with certain types of special centerlire cartridges has been exceeded `and misiires become excessive. While this may be overcome to some extent by a more powerful spring to obtain a higher total tiring energy, there yarises then still another problem, that of more likelihood of pierced primers and the resulting loss of obturation in the case.

While the energy can be increased by use of a stronger spring, .merely increasing the energy applied `for tiring provides no altogether satisfactory solution to the problem, even where piercing is avoided, because the resulting kick from the higher energy system has an adverse effect on the accuracy of aim.

In designing certain types of weapons, all within a desirable range of barrel bore calibers for utilizing a cartridge fitting in a iixed minimum size of cartridge chamber in the breech structure associated with the barrel, each increase in the caliber of the bore requires a corresponding increase in the size of the necked-down mouth of the cartridge case and ultimately frequent instances of mistire are encountered which cannot be attributed to piercing `or defects in the primer or cartridge.

A solution of the problem according to this invention involves reducing the weight of the firing pin while reducing `and maintaining the total energy utilized at the minimum level required. This gives the same effect as rigidity during application of the energy to the round to provide reliable ignition of the primer to substantially prevent excessive occurrence of misiires. There is marked Patented Oct. 2, 1962 improvement even in those instances of weapon design wherein the reduced neck of the cartridge is so enlarged as to leave an inadequate shoulder between the neck and the body of the cartridge case, thereby impairing the rigidity of the cartridge so much Athat the support for the primer fails due to liexing and shortening of the case. Apparently the base of such a round is displaced forwardly by the tiring pin blow so as to cause a cushioning eect which is the outstanding cause of misring. The lighter pin also makes possible a more rapid repeating action.

One object of this invention, therefore, is to provide an improved tiring mechanism construction which will not complicate such a gun appreciably, but which will materially improve the certainty and reliability of operation with even the most diiiicult to tire types of explosively tired cartridges.

Another object is to provide a tiring mechanism `adapted to improve the consistency of ignition in guns using cartridge cases characterized by relatively high deformability, whether such deformability arise from the pliant character of the material from which the case is made, or from the character of the shoulder back of the necking at the mouth of the cartridge case, or from the flexibility occasionally encountered in the base of certain types of cartridge cases such as those of shot shells.

Another object is the obtainment of a shorter action time for a tiring pin mechanism so as to permit a more rapid rate of tiring.

A still further object is the provision of a tiring mechanism requiring the least energy -for igniting a given primer percussively with consistency and making possible better accuracy of shooting.

Still another olbject is the provision of a tiring system adapted for cartridges having smaller bodies and shoulders relative to larger necks adapted for relatively large caliber bullets.

Still another object is to provide a new and improved firing pin construction characterized by lightness and preferably also by replaceability of the part of the pin subject to the most wear.

Other objects and advantages will appear from the description of a specific embodiment of this invention shown in the drawing wherein:

FIGURE l is a fragmentary elevational side view taken in cross section to show the front end of a tiring pin in accordance with this invention operatively associated ywith a cartridge case at the moment of striking the primer;

FIGURE 2 is a graphical depiction of the results obtained with this invention indicative of improvement in the firing action;

FIGURE 3 shows typical oscilloscope traces of various tiring pin pressure diagrams during an interval of time including the travel time of the pin; and

FIGURE 4 is a fragmentary side view of the front end of a monolithic light tiring pin having its point integral with its body.

In accordance with this invention it has been found that the sensitivity of primer ignition may be improved by making the tiring pin while maintaining its strength adequately lighter -and thereby increasing the tiring pin velocity and eiective striking pressure without increasing the total energy of percussion. In fact, with the same configuration and size of pin, this invention makes possible realization of effective percussion primer sensitivity just above the threshhold level but at a much lower level of energy than that heretofore believed necessary for liring. This improvement is maintained despite the inherently poorer rigidity of primer mounting encountered in certain ammunition rounds tried. In firing, the blow of the pin of this invention produces less displacement forward of Ithose rounds having an inadequate abutment shoulder between the body and the neck of the cartridge case. In any event, the effective striking pressure and reliability of ignition are increased regardless of whether the cartridge case is most rigid or quite deformable.

Specically, a lightweight tiring pin of this type having a wear and deformation resistant tip was found to result not only i-n a shortened action time, but also in an increase in reliability in functioning. This improvement provides reliable ignition even at a considerably lower kinetic energy level than that recognized as a standard for each of the various sizes of percussion primers now recognized as standards or known to those skilled in the art.

A pin having at least the major part made of a material considerably lighter than steel is contemplated provided the tip is maintained hard and tough enough for its purpose. One of aluminum with a removable screw threadedly attached steel tip provided a weight reduction of from albout 60% to 70% as compared to its heretofore used all-steel tiring pin counterpart. With substantially the same energy, one such lightweight pin provided an increase of from about 60% to about 65% in the prin velocity during the firing stroke. Using about the same energy of action, an aluminum steel-tipped pin took only 2.0 milliseconds to strike the primer while its steel counterpart required a travel time of about 3.0 milliseconds. This represents a reduction in tiring action time of about 16.

According to this invention, at least the main body of the tiring pin of a gun ring mechanism cons-ists of aluminum, magnesium, or their alloys, or of any suitable plastic such as nylon or Teiion. A metal such as titanium is also contemplated. When the point is a separate piece of steel, as for example, in the Reising U.S. Patent No. 1,313,912 and the Sedgely U.S. Patent No. 2,089,581, the remaining lightweight part of the pin constitutes most of the weight of the pin, preferably not less than about 95% of it. With a pin of very light material it is possible without any other change to increase the velocity of the pin by as high as about 80%, or even somewhat more, and to thereby obtain a more positive ignition of the primer and eliminate misfires arising from cushioning. Terminal velocity increases of about 40% or more are contemplated, and preferably at least 60-65%.

The material contemplated for at least the body of the pin is one having a density considerably less than that of steel, -i.e. lless than about .28 pound per cubic inch and preferably should be one of a density not in excess of about 0.2 pound per cubic inch. Materials having a density not in excess of aluminum and lightweight alloys of aluminum were found satisfactory. Light metals and their light alloys were found particularly desir-able because of the attendant strength characteristics. Aluminum and its alloys, which have a density of about 0.1 pound per cub-ic inch, therefore, were found especially suitable for the purpose. Plastic materials ysuch as nylon having a density as low as around 0.05 pound per cubic inch may also be employed provided they have the necessary strength. A minimum ultimate tensile strength of about 40,000 pounds per square inch is preferred.

If the body material has the physical properties needed in the tip, the Itip of the pin may be integral with the body. Such an integral struct-ure may consist of titanium or its suitable alloys. The tip may advantageously be made a separate part, in the form of a head or cap, provided it consists of a suiciently hard and strong material. It may consist of a suitable firing pin steel having the necessary yield strength and impact resistance as well as Ia minimum acceptable hardness, but any other material having comparabile resistance to deformation and wear is contemplated. Where the pin includes a separate tip, it is possible to utilize even harder materials than those heretofore employed because any deciency in the impact resistance is compensated for to a certain extent by the improved impact absorption capacity of the body materials contemplated, such as aluminum. For the tip, a material having a hardness of not less than albout 25 Rc Rockwell is contemplated. The tip material must be of such a strength as to be capable of transmitting without plastic `deformation an impact energy at a level of about 11/2 to 31/2 inch-pounds through the cross section of a cylindrical portion of the material having a diameter in the range from about 0.05 of an inch to about 0.1 of an inch.

In FIGURE l, there is shown an embodiment of the firing pin 1 mounted in a gun having a suitable size of cartridge chamber and a ried barrel bore having any caliber within a predetermined range, such as from about an 0.243 caliber to as high as about 0.358, for example. This higher caliber arrangement is shown, with part of a lower lcaliber round shown by interrupted lines for cornparison.

The pin consists of a body portion 2 and a separate tapered point 3, the apex of which is rounded preferably at a radius of about 0.045 of an inch to the configuration of a hemisphere. The point 3 has a screw threaded connection 7 and is made of a suitable steel treated to have suiicient hardness such as a Rockwell of about 50 Re together with toughness for the purpose. The whole pin together with the tiring pin spring 4 is carried in the bore of a bolt S which is `shown in association with a gun barrel breech structure 6 joined to a barrel portion 6a which has a bore at 17 of relatively large caliber for guiding and ejecting the relatively large projectile 8.

The gun barrel structure is Chambered at 9 for carrying a load 10 consisting of the projectile 8 and the cartridge case 11, the powder charge 12 and a primer 13 seated in the base of the cartridge case adjacent the face of the bolt for coaction with the ring pin point 3 as the latter passes out of the orifice 14 in the bolt face as the tiring mechanism is set into motion by release of the cocked spring 4.

The body portion 13 at `one end of the cartridge case includes the primer 13 and ts a fixed standard size of cartridge chamber 9. At the other end, the cartridge case has a necked-down portion 19 into which the projeotile 8 is snugly fitted Between the body portion 18 and the neck portion 19, the case is formed with a cartridge seating shoulder 20 ltapered for abutment with a mating shoulder 21 at the front of the gun chamber. These shoulders lend support to this type of cartridge case. This is particularly true when the gun is of smaller caliber and the round has a smaller caliber projectile 8a seated in a correspondingly smaller neck portion 19a inasmuch as the resulting tapered 4shouldered portion is lar-ger.

When, however, it is desirable to increase the caliber of the barrel bore 17 wi-thout increasing the case body 18, as by replacement of the front part 6a of the barrel to provide for the larger projectile 8, the larger bore shown in FIGURE l, shoulder portions 20 and 21 offer less support for the larger caliber round whereupon ignition with a conventional rliring pin of the type described becomes less reliable Ibecause of the cushioning action. With more generous support there is still some cushioning but it becomes less pronounced. Such cushioning action, nevertheless with various percussion primers is, therefore, one cause of more frequent occurrence of one type of misrre than is desirable at any caliber of round, and which the 4firing pin of `this invention virtually eliminates.

The composite pin shown in FIGURE 1 consists of an aluminum body 2 and a replaceably attached point 3 of steel which constituted only about 4% of the entire weight of one sample of the pin. As a result, the weight of one such pin 4according -to the embodiment of FIGURE 1 was reduced to about 27.66 grams as compared to about 67.70 grams for its all-steel counterpart. The weight of still another pin was reduced from about 62.91 grams to about 22.9 grams. With somewhat larger gun ring pins having proportionately `smaller points, and with materials still lighter than aluminum, the proportion of reduction in weight may be even larger. Since -it is desirable that at least the body 2 of the pin be made of a material which is as light as possible but which will still serve the purpose, even stronger plastics such as nylon, and other resinous materials, with or w-ithout iiber reinforcement, are contemplated. The point 3 is generally of a hardened, tough steel or of a suitable hard and tough titanium alloy. When the materials employed in the tiring pin 1 have suicient lightness together with sufcient hardness and toughness, the body 2 and point 3 may -be integral to provide a monolithic lightweight pin. Regardless of the details of structure, however, such pins in accordance with this invention provide advantageous results.

In FIGURE 2, there is depicted the results based on calculations derived from a test of a group of various typical percussion primers. A large number of samples of each of these was subjected to a tiring action at both different tiring pin 4speeds and tiring action energy levels. The number of mislires in testing were noted as encountered at the various stages of the test. With a suitable drop test apparatus, there were derived the energy levels in inch pounds and the average tiring pin velocity in inches per second necessary to give 100% ignition for each ltype of primer, designated as E, F, G, and H. The test was conducted with one tiring mechanism having a pin of given weight, designated as X, as well as with one twice as heavy, designated as 2X. The derived Values, graphically shown in FIGURE 2 for both the heavier pin and the light-weight one, are tabulated in the Afollowing table:

From lthis comparative data, it is evident that the primer can be red reliably and consistently at a lower energy level fwith the lightweight tiring pin than with the heavier pin. -In other words, the two firing mechanisms involve more than la mere dilference in velocity. Not `only is there an increase in Velocity along with the reduction in weight of the tiring pin, `but also notable -is the fact that the energy required to ignite lthe primer 100% of the time does not remain the same. With the lightweight pin, less energy is needed. In other words, the sensitivity of the primer has in effect been increased without need for a more sensitive primer, and therefore, more dangerous explosive ingredients in the primer. This, of course, makes -for a safer primer of reliable ignition and requiring less of a blow .from the tiring pin mechanism.

With the high-speed li-ghtweight ring pin of this invention, there is obtained a sharper impact characterized by a higher average effective peak pressure as detected by a piezo electric gauge arranged in such a manner as to indicate the magnitude of impact of the .tiring pin upon the entire cartridge case system. This makes possible a more dependable ignition of percussion primers, in all types of cartridge cases including those exhibiting the least deforma-bility such as, for example, the :steel cartridge cases.

Typical oscilloscope traces of the impact pressure produced by a slow steel pin, as well as by the tiring pin of this invention yis shown in FIGURE 3. This was recorded on a time base scale marked ed in units of 0.2 of Ia milli- 6. second using a ring having a pin tip contour generated by an 0.045 of an inch radius acting on a primer in a brass case. Trace A was taken an aluminum tiring pin having a steel tip, all of which together with its collar, weighed 27.66 grams. Trace S was taken with a standard steel firing pin, which together with its collar, weighed 67.70 grams. It is notable that the tiring pin travel time, and, therefore, the velocity of the lightweight pin are quite different from those of the heretofore known steel pin. Where it takes nearly three milliseconds before the steel pin strikes, it takes only about two milliseconds for the aluminum composition pin. The transfer of energy, which occurs in about 0.1 of a millisecond, is produced not only at a much higher velocity with the aluminum pin, but also is characterized by a higher peak pressure during the liring pin blow upon the primer.

Improved results were obtained with the lightweight pin at both low spring pressures as well as high spring pressures. Where the cartridge cases were of a deformable nature, `it was also observed that the collapse measured over the case length was less when the lightweight pin was used as compared to that noted when an equivalent heavy steel pin was used.

With both heavy and light pins like the aforenoted two firing pins, numerous tests were made on both brass and steel cases using both a weaker pin spring, designated as #4, and a stronger pin spr-ing, designated as #2, to determine the behavoir not only for readily deformable cases, such as those of brass and aluminum, but also with relatively deformation resistant cartridge cases, such as those of steel.

At the moment of impact with the primer, the lightweight pin of this invention has a much higher tiring pin velocity than the heavier steel pin. A steel pin, having a. weight of about 62.91 grams, was `found to strike ata velocity varying from about 132 inches per second with the weaker spring to about 139.2 inches per second with the stronger spring. The equivalent aluminum pin system according to this invention had a weight of about 22.9 grams and was found to strike at a velocity varying from about 218.4 inches per second with the weaker -spring to about 226.8 inches per second with the stronger spring. The firing pin energies with fboth types of prins were about the same. For example, with the #4 spring, the energy of the pins was about 31/8 inch-pounds.

The results obtained with these pins are tabulated in Table II as follows:

Table II Average Cartridge Case Firing Pin Pin Spring Peak Collapse Pressure (Inches) (psi.)

All Steel.- #2 Str0ng 1 8, 106 0. 00794 Aluminum-. do 2 8, 761 0. 00685 All Steek--- 1 13, 474 Nil Aluminum.w 2 13, 991 Nil All Steek--. 3 7, 242 0 00760 Aluminum-- 4 7, 911 0 00675 1 At tiring pin energy of about 3%0 inch-pounds. 2 At firing pin energy of about 3% inch-pounds. 3 At tiring pin energy of about 3% inch-pounds. 4 At firing pin energy of about 3% inch-pounds.

From the table, it is evident that with readily deformed cases such as those made of brass, aluminum and plastics, the lightweight, high speed ring pin provides a higher peak pressure with less collapse along the cartridge case, which means more reliable ignition. Even with the more rigid steel case, however, a better ignition is to be expected with the lightweight pin.

A composite p-in may include various advantageous combinations, such as the combination of a body of nylon with a tip of titaniferous metal substantially all titanium containing not more than minor` `amounts of alloy ingredients suitable for the purpose of this invention. A glass ber reinforced plastic body may be used. In any event, the major part, preferably about or more, of Ithe pin spear-:ae

d is constituted or the lightweight material; a firing pin of titanium base metal containing not more than small amounts of alloying ingredients, if any, is contemplated.

FIGURE 4 shows a pin 31 wherein the body 32 is integral with the striking point 53 as set forth hereinbefore and both body and point are of titanium base metal.

The lightweight faster pin of this invention is advantageous particularly with the more insensitive primers which appears more clearly in connection with FIG- URE 2.

While this invention has been described in connection with a bolt action firing mechanism of the type having a relatively long pin driven directly by a coaxially mounted firing pin spring when released by the scar, and in connection with firing centerre ammunition and other cartridges, it will be understood that those skilled in the art may make changes and modifications including those adapting this invention to various other types of tiring mechanisms and rounds including rimfire ammunition devices without departing from the spirit and scope of this invention as set forth in the appended claims.

It wil be understood that in accordance with this invention the spring of the ring pin also may be made of lightweight material. Instead of the spring steel of the type heretofore considered most lsuitable fo-r the purpose, a lightweight titaniferous metal may be employed to advantage. The lightweight material, however, is employed to best advantage in the pin inasmuch as reduction of the mass is more effective in the pin than in the spring.

What is claimed is:

l. A composite tiring pin of the direct spring actuated reciprocatable type having a body formed of aluminum and a striking tip screw threadedly secured to said body, said tip comprising a steel having a Rockwell hardness of about 50 Rc together with sufficient impact resistance at a minimum impact velocity of about 200 inches per second, said pin having a maximum weight of about 30 grams and said body constituting at least about 95% of the weight of the tiring pin.

2. In a gun-tiring mechanism for ignition of the percussive primer of a propellant cartridge, said mechanism including a reciprocatable tiring pin directly actuated by the spring action of a resilient member, the improvement comprising a firing pin the major part of which consists of a body formed of light weight material having a maximum density of about 0.2 pound per cubic inch whereby the weight of the whole pin is less than that of a oomparable pin of identical configuration of steel and having a striking point secured to said body, said point having a hardness and impact strength equivalent to a point of steel having a Rockwell hardness. notless than about 25 Rc, said hardness and strength adapting said point for striking said primer With a transmitted energy of impact in the range from about 11/2 to 31/2 inch-pounds, while resisting fracture and substantial plastic deformation of said point at a primer striking velocity of at least about 40% more than the velocity of said comparable pin, said body constituting at least 0.9 of the weight of the whole pin.

3. The firing pin of claim 2 formed as a composite wherein the light weight material has a maximum density of about 0.1 pound per cubic inch and the secured point is a separate piece of steel having a Rockwell hardness of around 50 Rc together with sufficient impact strength to resist fracture and plastic deformation at a primer striking velocity at least about 60%-65% more than the velocity of a comparable pin of steel.

4. In a percussion tiring mechanism having a direct spring actuated reciprocatable firing pin for ignition of the percussive primer of an explosive propellant cartridge having a case of deformable material, the improvement comprising a composite tiring pin having a body formed of material having a maximum density of about 0.2 pound per cubic inch and a separate striking point secured to said body, said point comprising a material of sufficient hardness and impact strength to adapt the pin for striking said primer with a transmitted energy of impact in the range from about 11/2 to 31/2 inch-pounds substantially and adapt said pin for resisting fracture and plastic deformation, said body of the tiring pin consisting of nylon.

5. In a percussive tiring mechanism having a direct spring actuated reciprocatable firing pin for ignition of the percussive primer of an explosive propellant cartridge having a case of deformable material, the improvement comprising a composite firing pin having a body formed of material having a maximum density of about 0.2 pound per cubic inch and a separate striking point secured to said body, said point comprising a material of sufficient hardness and impact strength to adapt the pin for striking said primer with a transmitted energy of impact in the range from about 11/2 to 3%. inch-pounds substantially and adapt said pin for resisting fracture and plastic deformation, said point consisting of a metal containing at least a predominate proportion of titanium.

6. In a gun-tiring mechanism for ignition of the percussive primer of a propellant cartridge, said mechanism including a recip-rocatable tiring pin directly actuated by the spring action of a resilient member, the improvement comprising a tiring pin the major part of which consists of a body formed of light weight material having a maximum density of about 0.2 lb. per cubic inch whereby the `weight of the whole pin is less than that of a comparable pin of identical coniiguration of steel and having a striking point secured to said body, said point having a hardness and impact strength equivalent to a point of steel having a Rockwell hardness not less than about 25 Rc, said hardness and strength adapting said point for striking said primer with a transmitted energy of impact in the range from about 11/2 to 31/2 inch-pounds, while resisting fracture and substantial plastic deformation of said point at a, primer striking velocity of -at least about 40% more than the velocity of said comparable pin, said body and point being integrally formed of titanium base metal.

References Cited in the i'lle of this patent UNITED STATES PATENTS 1,313,912 Reising Aug. 26, 1919 2,301,759 Stroup Nov. 10, 1942 2,324,775 Hentschel July 20, 1943 .2,724,303 Holcomb Nov. 22, 1955 2,736,119 Clarkson et al. Feb. 28, 1956 2,842,885 Hillberg July 15, 1958 2,847,786 Hartley et al Aug. 19, 1958 FOREIGN PATENTS l 96,326 Austria Mar. 10, 1924 480,580 Great Britain Peb. 24, 1938 

1. A COMPOSITE FIRING PIN OF THE DIRECT SPRING ACTUATED RECIPROCATABLE TYPE HAVING A BODY FORMED OF ALUMINUM AND A STRIKING TIP SCREW THREADEDLY SECURED TO SAID BODY, SAID TIP COMPRISING A STEEL HAVING A ROCKWELL HARDNESS OF ABOUT 50 RC TOGETHER WITH SUFFICIENT IMPACT RESISTANCE AT A MINIMUM IMPACT VELOCITY OF ABOUT 200 INCHES PER SECOND, SAID PIN HAVING A MAXIMUM WEIGHT OF ABOUT 30 GRAMS AND SAID BODY CONSTITUTING AT LEAST ABOUT 95% OF THE WEIGHT OF THE FIRING PIN. 